Introduction
Video conferencing has been used within higher education for over a decade and within the world of business for a while longer. The technology enables people to see and hear each other by using a combination of computer and communication technologies. Users can communicate at a distance, share the same computer-based workspaces and visually collaborate.
Videoconferencing can be described as a method of conferencing between two or more locations where both sound and vision are conveyed electronically so as to enable simultaneous interactive communication.
It is perceived as a new, fast growing medium with the potential to save significant amounts of money in terms of both travel costs and time. It can also open up new methods of communication e.g. linking many international sites together simultaneously.
Videoconferencing is certainly growing very rapidly, and can save a great deal of money but it is not a new technology. Videoconferencing has been with us for decades. Multinational corporations have been routinely using it since the 1980s. Television broadcasters have used two-way studio interviews (for sports coverage etc.) from the 1960s and probably earlier. In this case the viewer acts as a passive participant, viewing the interaction between the link person and a presenter at, for example, a remote football ground. These two are actively videoconferencing, but are not normally considered in this light. This type of conferencing is achieved at a high technical standard with broadcast quality sound and pictures.
So why has videoconferencing suddenly over the last five years become topical and much more popular? The main reason is the availability of equipment at a reasonable cost. The two examples outlined above demonstrate early applications but they both used dedicated methods of connection between the sites. Dedicated connections are very expensive so the need had to be overwhelming to justify the cost.
The introduction of dial-up digital connections by the telephone companies and access to the Internet has now made the cost of connection to remote sites affordable to a much wider group of users.
Videoconferencing can conveniently be broken down into 3 components:
· The conference environment, i.e. the room or studio;
· The conference equipment, which generates sound and vision signals from the participants
and converts these into a format that enables transmission to a remote site over the network;
· The conference network that links the sites together.
All videoconferences must have these three basic elements - however simple or complex, the conference can always be divided into environment, equipment and network.
Conferencing is not limited to talking heads (i.e. the participants). Still images, e.g. 35mm slides or overhead transparencies, can be introduced to illustrate a particular point. Moving sequences from a videocassette may be replayed. An application running on a PC, e.g. PowerPoint or Word, can also be relayed. It is even possible for a PC application running at one site to be shared with another site so that the remote site can annotate and take control of the software. When PC documents are shared in this way it is termed “data sharing”.
What is Videoconference?
The translation of "videoconferencing" in dictionary terms means "the holding of a conference among people at remote locations by means of transmitted audio and video signals" and as "conference" translates into "a meeting of two or more persons for discussing matters of common concern" we can see that this is a useful tool indeed.
Videoconferencing basically means that you can sit in front of a video monitor (a TV screen) talking to another party in virtually any part of the world. This is not limited to two persons in conference and may involve many people at many different venues around the world.
Videoconferences are not limited to the exchange of pictures of the participants. Depending on the videoconferencing technology used it may be possible to switch in a video player or a document imager. Some venues now also have data sharing alongside the videoconferencing equipment and so it is possible to share PC based presentations or web pages along with a host of other popular applications.
There are two video conferencing configurations available:
Analogue video conferencing employs conventional telephone lines and uses a modem to interface the computer to the network. Digital video conferencing uses ISDN2, and is of a higher quality than analogue systems, providing higher definition pictures and faster data transmission rates.
Both systems can operate using conventional conductive materials to transmit and receive. This normally means 'copper wire' systems, used by the nation's telecommunications infrastructure. Increasingly however, major providers such as British Telecom and Mercury have committed to installing photonics based or fiber optic cable technology. This technology has proved to be faster in terms of speed of data transmission, and offers greater bandwidth available for data traffic. This means that computer data, text and graphics, sound, video and fax can all travel along the same digital highway simultaneously (Hilton, 1996).
The standard desktop videoconference system resides in a stand-alone p.c., and consists of a camera, p.c. card, application software and telecommunications links. Analogue video conferencing configurations also require a modem and conventional exchange line connection.
A typical meeting brings people face-to-face to discuss a need, a problem, or a plan. People come from various locations to one place to conduct a meeting. These people normally work in the same building or, more likely, in a distant location and must travel to participate in the meeting. Video conferencing enables a face-to-face meeting to be conducted without all the players having to leave their place of business. You can look at video conferencing as an electronic meeting where participants interact with other participants through the use of various pieces of video equipment.
With a typical video conference, pictures and sound from one location are transmitted to one or more other locations by a camera and microphone. These images are fed through a coder/decoder (or Codec). A Codec is a specialized piece of equipment that compresses and converts the video signal from analog to digital and sends it over specific phone lines to the other video conferencing sites. The Codec on the receiving end decompresses the incoming digitized images and converts them to their original form. The amazing thing about this process is that it occurs in real time, immediately, without any hesitation.
Why we use it?
1. Seeing is believing
Video conferencing is simple: callers see each other on a screen and talk! Groups of people can share conversations, hold a meeting or attend a class where everyone can see and talk to everyone else. Participants can also share access to material and work collaboratively on documents, spreadsheets, project briefs and diagrams. Video conferencing is popular because it's interactive, it's live and it's natural.
2. Visuals are appealing
Does the ability to see the other party really add to the interaction? Yes! That's why the telephone isn't enough.
Psychologically we like to interact on a more personal level and videoconferencing allows personal contact in meetings and lessons, in a location of our choice. We no longer have to travel distances to attend meetings or miss study opportunities because we live too far from a major centre. Virtual face-to-face classes and meetings are possible whether the participants are in the same locality or another country.
3. Trends
Around the world schools, colleges and libraries are using videoconferencing technology to:
§ Provide equitable access to resources for at-risk or special-needs students
§ Share scarce resources, especially for scattered or rural populations
§ Deliver information on rapidly changing topics
§ Provide a virtual experience when the real experience is not feasible
§ Facilitate collaboration, information sharing, problem solving and decision making within a learning environment based on shared discussion, expertise and problem solving.
Videoconference environment
These recommendations are intended for organizations planning the installation of a small to medium sized conference room, accommodating up to 20 persons. The principles apply to most videoconferencing situations, but teaching to large groups of students (more than 100) in a lecture theatre brings particular problems associated with the delivery of satisfactory sound and television pictures.
The participants at the local site need to see and hear clearly the participants at the remote site (and vice versa), so the important equipment items are: television cameras, picture monitors, microphones and loudspeaker/amplifier units. The size and layout of the room are also important factors.
For a small group, e.g. six persons, one large screen monitor (70 cm diagonal) will produce an image large enough to be viewed comfortably by everyone. For 20 persons a much larger image or several smaller viewing monitors will be needed. The size of the room will dictate the size and power output capacity required for the loudspeaker/amplifier units. Camera position and the type of camera lens are also dependent on room layout, as is the placement of microphones.
Videoconferencing from large lecture theatres poses a much greater challenge than videoconferencing from a meeting room. Sound amplification is normally needed to provide adequate coverage for the theatre microphones and sound sources (e.g. video replay) in addition to that required for the remote conference sound. The reverberation time (i.e. the amount of echo in the room) is usually also much greater than in a small room. These two factors militate against effective conferencing by increasing the tendency for acoustic feedback (i.e. howl-around) and introducing an amount of echo that normal videoconference echo cancellers cannot handle.
Effective sound pickup from a lecture theatre audience is extremely difficult unless a roving or highly directional microphone is used, both of which require an operator. A large audience will also require a very large picture image to view the remote site, such as that provided by a video projector. As the image produced from such projection is significantly less intense than that produced from a conventional picture monitor, the ambient room light will need to be dimmed for acceptable viewing. Unfortunately the lecture theatre video camera (providing audience images to the remote site) requires a fairly high level of lighting to produce good quality pictures. The introduction of lecture theatre video/data projectors with a light output of 3000 ANSI Lumens may allow the auditorium lights to be operated at a suitable level to provide adequate pictures from the lecture theatre. In addition automatic cameras will not normally produce an accurately framed image of members of the audience, so the cameras will need operators if close up images of audience members are required.
Sometimes videoconferencing sessions need to be relayed to large lecture theatres where the audience is passive observers. In this case, only sound and vision signals from the remote site need to be transmitted to the lecture theatre for reproduction and display. This is much easier to achieve: it is when interaction (i.e. return sound and vision) is required from the lecture theatre environment that the main problems arise.
The environment for videoconferencing requires particular attention if the highest quality sound and vision signals are to be transmitted and received. This is equally true whether sophisticated, dedicated videoconferencing equipment or the simpler desktop plug-in cards are being used.
The requirements for large group teaching are much more demanding than those for straightforward meetings, but the basic principles remain the same. In the interests of simplicity, only videoconferencing rooms used for meetings will be considered in detail here, but where it is felt that points relevant to a teaching network are important these will be specifically mentioned.
Where an integrated videoconferencing system e.g. a rollabout or set top box has been purchased and installed then not all of the following will be applicable. Some information has been included to assist those sites designing their own system around a separate CODEC (COder/DECoder).
To achieve good results certain room parameters need to be controlled quite tightly, especially those affecting noise intrusion, internal reverberation (echoes), and lighting.
To provide an effective environment for videoconferencing requires particular attention to the room’s characteristics. This is true for both sophisticated room based systems and desktop units utilizing plug in PC cards.
The room needs to be quiet, as microphones can accentuate unwanted sounds. The human ear may be quite tolerant of ambient noise such as traffic, air-conditioners, students in corridors etc. but a microphone is not so discriminating and the intrusive noise can effectively render a conference unworkable.
Echoes within a room (or reverberation) must be controlled otherwise the conference sound will be degraded.
Television cameras are sensitive to changes in light levels so windows pose a special problem. The overall lighting level also needs to be high to produce the best possible images from the camera.
Videoconference equipment
In its most basic form a videoconference transmits the images and the voices of the participants to a remote site. Optional image sources include still images and/or video programs. Data from a PC may also be provided.
The basic conference requires a:
- Television camera to capture images of the participants;
- Microphone to pick up their speech;
- Means of transferring this sound and vision information to the remote location.
The Television camera and lens
The camera converts light images into an electrical signal so that it may be displayed, recorded or transmitted. The camera lens focuses the images onto a light sensitive layer sometimes referred to as a Charge Coupled Device or CCD.
The type of lens determines the angle or field of view. A wide-angle lens can capture a large group, a narrow-angle lens a close up. The ubiquitous web-cam is a very low cost (and low quality) single chip camera with a fixed focus lens designed only to provide an image of the PC operator. Lenses suitable for group conference applications will have a variable field of view. These are known as zoom lenses as they can zoom out to a wide-angle shot to include a group or zoom in to a close up shot of a single participant.
The sensitivity of the lens is determined by the amount of light entering the lens most camera lenses can vary the amount of light either automatically or manually.
Both methods move an iris diaphragm in front of the lens to effectively increase or reduce the diameter (or aperture) of the entry pupil of the lens. Most cameras control the iris automatically to optimize image quality for the available light. It is important to realize however, that in low light conditions as the iris is opened up to compensate there will be less depth of field. The resultant picture may not appear sharply focused overall.
Television cameras are capable of operating in very low light conditions but they produce much higher quality pictures at higher light levels. At high light levels the lens aperture will also be reduced to give the added advantage of a greater depth of field. In broadcast television this increase in depth of field may not necessarily be seen as an advantage. Directors may require the foreground to be in sharp focus with the background out of focus, for artistic effect. This gives separation to the images. However in videoconferencing the more depth of field the better is generally the rule.
Microphones
A microphone converts sound energy into an electrical signal to enable it to be recorded or transmitted to a remote location. It has already been mentioned that microphones pick up unwanted sounds together with the participants’ voices. If these unwanted sounds are significant they will interfere or even completely obscure the desired parts of the sound. The correct choice of microphone and its position in the room are vital to achieve high quality sound. The conference environment will also influence sound quality. As has been mentioned above both low ambient noise levels and low levels of echo are essential requirements.
The CODEC
The CODEC has two components the COder and the DECoder. The COder takes the local sound and vision signals and converts them into a form that can be transmitted over a digital network. The DECoder performs the reverse function i.e. it takes the remote site’s digital signals from the network and converts or decodes them into a form that enables the local picture monitor to display images and the loudspeaker to radiate sound from the remote site.
CODECs can be packaged as plug in PC boards for personal desktop use, within purpose designed complete systems for group conferencing known as “Roll about”, or as compact “Portable” units that sit on top of picture monitors.
The electrical signals generated by the camera after amplification is suitable for recording. They may also be displayed on a monitor. Similarly microphone signals can be recorded or heard via a loudspeaker. These electrical facsimiles of the sound and picture are termed analogue signals. Analogue television signals require a network with a large capacity for transmitting the information, i.e. a wide bandwidth network. The sound and vision signals in this form are sometimes referred to as base-band signals. Base-band analogue networks are capable of very high quality but can be very expensive to install. They also generally need a dedicated circuit i.e. only available between specific sites for a particular application. For a short link, e.g. between rooms, dedicated circuits are cost effective as they can be achieved simply by a length of cable, but for anything further the costs can be prohibitive.
Videoconferencing using analogue methods was established by multinational companies in the 1980s, and it was also employed by the broadcasters for sports interviews and the like. The potential cost savings (to multinational companies) and the importance of the message (broadcasting) outweighed the high network costs involved.
For videoconferencing to appeal to a wider audience it had to prove cost effective. This was solved by the arrival of digital networks that were easily accessible. Analogue and digital signals are very different. Human senses respond directly to analogue stimuli. A typical example of an analogue signal is shown in Figure 3, the sound wave generated by a vibrating tuning fork. A microphone close by will convert the sound variations into an electrical signal that mimics the original. The microphone signals vary both in level (amplitude) and frequency (pitch) depending on the sound being picked up. The electrical signal is a facsimile of the sound wave. Analogue networks therefore need to respond to both amplitude and frequency variations to transmit the information accurately.
Digital signals are transmitted as a series of electrical pulses that vary in sympathy to the original signal in various ways, (depending on the digitisation system in use). The level or amplitude of the pulses is of no significance. The presence or absence of a pulse only needs to be detected. Digital transmission is thus much more tolerant of poor networks.
Video conferencing equipment is made up of the following pieces:
- Camera
- Monitor
- Microphone
- Codec
What type of equipment is used and how it is placed depends on how your video conference system will be used and who will be using it. There are three basic types of equipment setups, which must be H.320 standards compliant that are used depending upon the type and size conference you need to conduct.
Room Systems are designed for video conferences where a large number of people will be viewing or participating (for example, training sessions, group meetings, etc.). Rooms are dedicated for video conferencing with multiple monitors and cameras usually built in to the walls. These rooms are usually custom-designed specifically for this application.
Roll-About Units, which are the most popular, are best adaptable for smaller group meetings or conferences. These units consist of one or two monitors, contained in a cart, which houses the Codec, camera, and any other peripheral equipment. This setup can be placed in an existing conference room with network access as its only limitation. Again, you will find that the roll-about setup is the most popular form of video conferencing.
Desktop Systems enable personal computers to be equipped with a camera and microphone as well as software and boards in order to conduct a video conference from an existing personal computer. The PC can be connected with one or many sites, but it is best suited for one-on-one conferences.
Room design
Location of Room
A quiet, convenient and central location is to be preferred. High levels of structural and airborne noise will be a problem so the room needs to be located away from sources of noise such as traffic, lifts, plumbing, workshops, plant rooms, air conditioning ducts, etc. Sounds that are a minor irritation to the ear can become unbearable when picked up by a microphone. Access should be suitable for persons with a physical disability. A ground floor location is normally preferable.
Room Size
This depends very much on the number of participants involved. From our experience most meetings will involve only 3-4 people although, on occasions, larger groups are involved and the room should be capable of seating a minimum of 12 people. For teaching seminar groups accommodation for 20 students may be required whereas teaching involving 100 or more students is more likely to take place from a lecture theatre.
Room Shape
To reduce undesirable acoustic effects square rooms should be avoided if possible. An oblong or irregular shaped room is a better shape as it does not encourage standing waves (and thus echoes) so much. Rooms with non-parallel opposite walls are good acoustically, but unlikely to be found in practice.
Room Layout
Room layout will depend on the number of participants, the available space, and the purpose of the room.
Meetings
In the meeting scenario, television cameras are positioned close to the viewing monitors so that participants are normally looking in the direction of the camera lens; this produces natural and expected images at the far site. Two picture monitors (televisions) are advantageous to view both transmitted and received images simultaneously.
Figure illustrates the horseshoe arrangement of seats, which permits a clear view of each participant, but some panning of the camera will be necessary to optimize results; for small groups this layout can work very well. Double horseshoes (i.e. one behind the other) can accommodate medium sized groups and still permit a reasonable camera image, especially if the seating positions on the second row are staggered.
Where space is very limited several parallel rows of tables (Figure 2) would house the maximum number of participants, but the camera will not be able to pick up everyone clearly.
Another disadvantage of parallel tables or double horseshoes is that this arrangement tends to inhibit interaction at the local site as people have to turn around to talk to the participants in the rows behind.
During a conference, local interaction can be just as important as interacting with the remote site. A single horseshoe of 20 people would, with a suitable camera, allow a clear view of everyone and allow efficient interaction but would need a large room.
Layout is thus a compromise between a clear view, interaction and the space available.
Teaching
Videoconferencing teaching sessions can take many forms including:
Ø A lecturer in a studio teaching remotely to a group of students
Ø A lecturer teaching students locally and also relayed to a remote audience
Ø A lecturer teaching local and remote students with full interaction
In the first scenario the lecturer can adopt a seating position in one of the meeting configurations above. They can select appropriate sources i.e. camera, visualiser, video cassette player as needed for the presentation. They can also interact with the remote site in the same way as would occur during a videoconference meeting.
The second situation requires a different approach. If a local teaching session to a group of students is also simultaneously relayed by videoconferencing to a remote site then the room arrangement needs to be modified. The lecturer will need to face the local students but also be seen clearly at the remote site. The room layouts illustrated above are clearly not satisfactory. A second camera focused on the lecturer will be required. The lecturer will also need to view his or her picture together with any illustrations they are using e.g. PowerPoint slides while facing the local audience. This can be achieved by providing a preview monitor in the lectern as shown below. As the lecture is simply being relayed to the remote site, interaction is not expected, so their pictures and sound are not relevant.
Thirdly, where teaching is being conducted both locally and remotely and full interaction is needed, we have a more complex situation. Pictures and sound are now required from the remote site. The local students and the lecturer will need to see and hear the remote students. A second television display facing the students will normally be provided, but the lecturer also requires a second preview monitor in the lectern facing them in order to view the remote students.
Television picture monitors have been illustrated but in many cases data projectors will be utilized for the student displays as the images can be much larger than television monitors and still be acceptably bright under ambient lighting levels. However, care has to be taken with some data projectors, as the noise from their cooling fans can be quite intrusive.
Room Decor
Television cameras have very limited contrast-handling ability, so wall decoration should be neither too light nor too dark. Mid-tones tending toward light (e.g. cream or magnolia) are to be preferred, to give the room a bright atmosphere. If the walls are to be painted, a matt finish will minimize reflections. Grey walls can create a rather dull background, and shades of red or any other fully saturated color should be avoided.
Strongly patterned wallpaper or ‘busy’ curtains will only distract the viewers; mid tones and plain textures are much more suitable. Curtains should be loosely gathered, otherwise camera auto focus systems may focus on the vertical edges of the curtain folds rather than on the participants.
A college crest hung behind the participants against a plain wall can add interest to the image although during multipoint conferences most crests can look very similar and some additional identification will be necessary.
Videoconferencing equipment, and in particular the vision CODEC, compresses the vision signal considerably (over 1000:1 for 128 kbit/s data rate) to send the signals over the ISDN or IP network. Patterned backgrounds contain more spatial information and thus more detail than plain walls and so force the CODEC to work much harder, whereas plain backgrounds allow the CODEC to concentrate on more important picture areas, e.g. the participants’ faces.
Furniture
Individual sites will have their own preferences for the type of furniture to be installed. Try to avoid bright, reflective surfaces that may cause unwanted highlights in the picture and distract the viewer from the main subject matter.
Control desks/tables will need to accommodate the likely number of participants but also provide space for: the CODEC remote control unit, the microphones or audio units and a visualiser to permit the display of diagrams, x-rays, overhead transparencies, etc. For data exchange a PC will also be needed.
In more complex installations, space will also be needed for a vision mixer/switcher to select vision sources and remote controls for additional cameras if these are required.
Conference Equipment
If picture monitors displaying local and remote pictures are built in to cabinets, then allowance must be made for adequate ventilation and for easy access for maintenance, etc. A comfortable viewing distance from eye to picture monitor is 5-6 times the picture diagonal.
A telephone is essential; this could be fitted with a flashing light instead of the conventional ringing tone to avoid disturbance during conferences. A quiet, accurate clock that can be easily read but is not in shot will also prove very useful.
In complex installations, an audio mixer is used to interface the many items of audio equipment to the CODEC. The mixer has the facility to adjust the relative levels of the microphones and other sound sources, but this is to be discouraged during a conference. Echo cancellers in the CODEC align themselves within the conference to an optimum setting to minimize echo, a process which is termed “training”. Microphone and loudspeaker levels should therefore not be altered once a conference has begun as any variations will upset the echo canceller’s original alignment and cause it to retrain, which could disrupt the conference. By locating the mixer away from the desk any temptation to alter microphone levels is minimized. A desk mounted microphone mute facility is necessary to kill the local sound during a conference so that the participants may talk discreetly without disturbing the remote site.
Windows
Windows always cause problems for television cameras due to the changing lighting levels. A room without windows is to be preferred. If windows are inevitable (perhaps in a multi-purpose room) then adequate blackout must be provided to exclude all natural light. Roller or vertical blinds are seldom successful and heavy curtains or drapes are much better. These will also assist in improving the acoustics (and the decor).
Lighting
Modern television cameras are very sensitive and will operate in quite low levels of illumination, but providing high lighting levels will produce a much better picture.
Tungsten/Halogen lighting is normally preferred for television, but in the videoconferencing environment it is unsuitable due to the amount of heat it generates. Fluorescent lighting is the only realistic choice: it is energy efficient, dissipates little heat and is relatively inexpensive.
Normal office lighting levels will be adequate, i.e. 500 Lux, and an intermediate or warm fluorescent tube color (equivalent color temperature 3200-4000 Kelvin) will give acceptable pictures and emit a fairly comfortable light for the participants.
Fittings should be arranged so that a higher level of illumination is produced in front of the participants than either above or behind them, so as to prevent shadows on faces. Fluorescent lighting, though not ideal, will give good, even, energy efficient illumination. Care needs to be taken to avoid glare from the fluorescent tubes on the picture monitors. One solution is to use visual display unit (VDU) lighting, which is fitted with diffusing shades (i.e. category 2 or 3 lighting). It is also helpful if lights in the vicinity of the picture monitors can be switched off independently of the general lighting.
The light intensity emitted from fluorescent fittings is not equal in all directions, i.e. it is brighter parallel to the tubes and less bright from each end. When planning room lighting, care must be taken to ensure the participants are lit adequately.
Dimming systems, especially the less expensive systems, can cause interference to microphone circuits due to radio frequency radiation. Unless suppliers can guarantee their equipment will not cause problems, it is wise to avoid dimming and to arrange for the lights to be switched in rows. High frequency fluorescent systems provide quiet and flicker free illumination but they also have the potential to interfere with the audio circuits.
To warn others that a videoconference is taking place an “On Air” light outside the room is a useful addition.
Acoustics
It has already been mentioned that the room needs to be situated in a quiet part of the building away from lifts, noisy plumbing, traffic and the like. This type of noise that is transmitted by the structure of the building is very difficult to eradicate. It is termed “structure-borne” noise.
Noise levels may be measured with suitable sound pressure level (SPL) meters but the results need to be interpreted very carefully. The suitability of a room for conferencing is a decision best entrusted to an experienced person, as the acceptable level of intrusive noise is dependent upon the nature, as well as the level, of the noise. As a guide for videoconferencing, the recommended SPL reading for television studios is around 35dBA. The “A” refers to the weighting used during the measurement, and takes in to account the response of the human ear to sounds of different frequency. The SPL makes a single measurement. A more accurate assessment of intrusive noise is achieved by plotting a “Noise Rating” (NR) curve. This requires an instrument that measures the noise at a number of spot frequencies. Architects are familiar with Noise Rating curves as they use them in the design of buildings. For television studios an NR of 25 or lower is required. Radio studios are more critical with figures of 30dBA and NR of 20. Videoconferencing rooms should aim for an SPL of 35dBA and NR25.
In practice these figures may have to be relaxed a little, but then there is the added risk of noise intrusion into a conference. A little noise, although audible, may be tolerable during some conferences but it is better to aim for a high quality environment from the start.
Attention must also be paid to the internal acoustic characteristics of the room. Too much reverberation (echoes in a closed room) will present problems. The room should not be too absorbent, however, as this will present an unnatural and uncomfortable environment for the participants.
Carpets and other soft furnishings will improve the acoustics effectively at high and middle frequencies and will generally be more cost effective than acoustic ceiling tiles. Hard, blank walls can be deadened by heavy curtains, which also improve the decor. Upholstered chairs will also help.
Where a room suffers badly with echoes it is far better to treat adjacent walls than two opposing ones: thus standing waves will be reduced in two dimensions (length-wise and width-wise) instead of just one.
To remove low frequency reverberation is considerably more difficult. An effective method is to include some resonant cavity absorbers, as designed by the BBC. See VTAS “Audio Engineering for Videoconferencing” (GD/VTAS/006) document for more details.
Heating and Ventilation
Participants may be videoconferencing for considerable periods, so it is essential that they are comfortable. Normal office temperature levels (i.e. 16-210C) and comfortable humidity levels (40-50%) should be maintained.
Microphones are extremely sensitive to moving air so, although normal air conditioning and heating systems may operate unnoticed by the participants, the microphone can amplify the effect and cause unacceptable interference during a videoconference.
Broadcasting studios use specialized air conditioning systems that move a large volume of air very slowly through large ventilation ducts and so create very low levels of background noise.
Conventional heating/air conditioning systems use low volume/high velocity systems through small ducts: these are inherently noisy, but also much less expensive to install. It is unlikely that a low velocity system will be installed because of the cost.
What is important is the ability to control the system independently if necessary during conferences. The integrated air conditioning systems that heat/condition whole floors or groups of rooms cannot usually be controlled adequately in individual rooms and will inevitably introduce unacceptable background noise that will be uncontrollable.
Electrical Power
Safety Issues
All electrical installations will need to comply with the IEE wiring regulations and be carried out by competent and qualified staff.
A master switch fitted with an earth leakage breaker is a convenient way to isolate all videoconferencing equipment.
The vision and sound equipment, together with the CODEC/echo canceller, have fairly modest power ratings and 13 amp domestic sockets will be adequate provided the earth and clean supply stipulations outlined in 2.12.2 are met.
Signal cables should not normally be laid in the same cable duct as 240-volt a/c mains supply cables (see IEE regulations).
Electrical/Electromagnetic Interference
The equipment used for videoconferencing should be powered from a clean mains supply to avoid electrical interference. It should not be on a circuit that is shared by large electrical loads such as plant motors, lifts, workshops, etc.
Local mains interference filters (e.g. on socket outlets) can help in some cases, but it is far better to start with a clean supply than to attempt to correct a dirty one.
The signal earth ideally should be separate from the normal electrical earth, i.e. a clean technical earth. (It is imperative to comply with IEE regulations.)
All equipment should normally be powered from the same electrical power phase. If this is not possible (e.g. where equipment is located in different rooms or buildings) then precautions will need to be taken to isolate the audio and video signals to avoid mains hum interference. See VTAS document “Audio Engineering for Videoconferencing” (GD/VTAS/006).
To minimize hum pickup, signal cables (i.e. sound and vision) should not be run parallel to mains supply cables; this is especially important for microphone cables.
Cable Ducting
Several cables will need to be run from the control desk to the picture monitors and loudspeaker/audio mixer and also to the CODEC wherever these are situated. Some provision must be made for small ducting or conduit to protect these cables.
When cable runs across floor spaces cannot be avoided, then some form of protection must be provided. Special rubber cable protectors are available that protect the cables and minimize the risk of tripping. A list of suppliers can be found in Appendix B. At the very least the cables should be secured with marker tape.
Standard
The standards organizations:
There are numerous bodies defining telecommunications standards, but the principal ones relevant to videoconferencing are:
- International Telecommunication
- American National Standards Institute (ANSI)
- International Standards Organization (ISO)
- International Electro technical Commission (IEC)
- Internet Engineering Task Force (IETF)
· European Telecommunications Standards Institute (ETSI)
The standards:
Networks and Standards
H.3xx Videoconferencing Standards
Mandatory Standards
Videoconferencing Sub-Standards
Video Coding Standards
Audio Coding Standards
Structure for Communication (i.e. data stream formats)
Still image transfer formats H.261 Annex D and T.81
ITU-T Sub standards applied to an H.320 CODEC
T.120 Document and Data Sharing Standard
T.120 Sub Standards:
Other Standards
JPEG
MPEG-1
MPEG-2
MJPEG
The Network
The relatively new digital networks that have been introduced over the last decade have encouraged the current expansion in videoconferencing. They have made the medium affordable to a much wider market.
Integrated Services Digital Network (ISDN)
This is a method of using the existing telephone infrastructure to carry digital signals. Offered by telecommunications providers it is now available in many parts of the world. The service is accessed through dial-up in the same way as a telephone so the network does not have to be dedicated between the videoconference centres. The costs include installation (for the special interfaces), rental and call charges. The quality of ISDN conferencing is limited by the quality (or bandwidth) of the connection, varying from 64kbit/s (ISDN-1) to 2 Mbit/s (ISDN-30). The normal bandwidth used for meetings is either 128kbit/s (ISDN-2) or 384kbit/s (ISDN-6). One important feature of ISDN is its Guaranteed Quality of Service (GQoS), which means that if for example a 384kbit/s link is dialed then unless there is a fault condition the full 384kbit/s will be provided for the duration of the conference. Some other networks e.g. the Internet are currently unable to offer Goes because of the way the data traffic has to compete for space.
High quality digitization of a television signal would require a network working at a speed of around 270Mbit/s. As a typical ISDN or other videoconferencing network digital network can only pass 384kbit/s, we have a serious problem. The signals have to be reduced or compressed in order to fit the available commercial networks. The CODEC (see 8.3 above) enables this to occur and the process is called encoding. At the remote site this coded signal has to be decoded to reconstruct the original sound and vision signals. The term CODEC is derived from the devices ability to Code and Decode the signal.
The Internet
Most academics in Further and Higher Education have access to the World Wide Web (WWW) via the Internet. The method of connection can be via the institutions' Local Area Network (LAN) through Metropolitan Area Networks (MANs), which link regional institutions together, or more commonly through the LAN/MAN to JANET, and then to the Internet. From home, access is usually via a service provider (such as BT) using the telephone connection. Service providers then link to the WWW.
The common factor between all of these networks is the standard used to transmit/receive the information. They all use the Internet Protocol (IP) standard to ensure information passes flawlessly between networks. The success of the WWW could not have been achieved without this single standard.
A disadvantage of IP transmission is that all data traffic, e.g. e-mails, WWW downloads or videoconferencing, has to share the same pipes, so they all have to compete for the available space or bandwidth. With e-mails and WWW downloads this may cause delays between sending and receiving data dependent on the traffic, but all of the transmitted data should arrive eventually at its destination even though some parts of the data may have taken different routes before finishing its journey.
Videoconferencing is not so tolerant. Videoconferencing transmits digitized sound and vision signals and both are very intolerant of missing or delayed parts of the data. When a network is congested and some parts of the data are routed via an alternative but longer path the recovered sound or vision can be impaired. The degradation in quality may vary from a missing speech syllable and image fuzziness to completely incoherent speech and an unrecognizable image. IP transmissions do not guarantee quality of service at present.
Broadband Networks
Computers connected to the Internet via a telephone line are limited to a data rate of around 56kbit/s. If higher speeds are needed then the telephone provider may be able to install ISDN digital lines with speeds from 64kbit/s to 2Mbit/s. When numerous data streams from subscribers converge to travel to other towns or countries very high capacity networks are needed purely to cope with the density of data. Super JANET, the backbone of the JANET network, offers a capacity up to 2.4Gbit/s, although connection to many sites is at a somewhat lower speed.
Alternative methods of transmission may be used when the network can provide sufficient capacity. MANs generally have a large data handling capacity. The Scottish and other MANs have used a system of transmission called M-JPEG (Motion JPEG) over ATM (Asynchronous Transfer Mode). This combination can provide very high quality approaching broadcast television.
Types of Videoconference
Person to Person (or Class to Class):
This is the simplest form of conference where two computers connect directly with each other using CU-SeeMe software or some other conferencing software. All you have to do is type in the IP address of the person or class you would like to connect with for a conference. Much the same way you would dial up a friend on the phone.
Group Conference:
This is where many people can participate and collaborate. To do this, each person or class has to connect to a site that is running Reflector software. The connection is made by typing in the IP address of the Reflector. The Reflector receives everything that is transmitted by the group and then transmits it to the others in the group.
Broadcast:
This is one-way conferencing much like television. One computer running Reflector software transmits audio and video to all those who are connected. NASA TV is a good example. You can tune to NASA TV by connecting via CU-SeeMe to IP Address: 139.88.27.43 or IP 129.186.112.242.
Compressed digital video over ISDN lines:
High quality video conferencing operates on ISDN lines at a minimum of 128 kps. A computer compresses the video signal allowing it to be transmitted on ISDN lines and the quality of the video is determined by how much you want to pay for the service. The lowest speed is 128kps, but multiples of 265kps or 384kps provide two-way video of almost broadcast quality.
Compressed video conferencing can be combined with other media: text and graphics can be transmitted by a document camera, computer graphics or streaming video clips can be transmitted and viewed, and participants can join in by audio alone.
There are desktop and room systems appropriate to individual or group needs. Both audio and video interaction is 'seamless' and enables both parties to see and edit documents simultaneously while working on them. Body language and facial expressions are integral to the interaction, providing the same advantages as a face-to-face meeting.
The desktop models, the portable or roll about systems and the room systems are all easy to use and do not require a high degree of technical literacy. Multi-point conferences are possible and there are products available with in-built conference bridges for connecting two or more sites together. ISDN videoconferencing conforms to the H.320 international standard.
POTS video conferencing
Video conferencing over normal telephone lines has been available for several years and proved a reliable medium for the delivery of education to rural and isolated schools and individuals. A connection is established through a modem usually running at 28.8K and higher. It conforms to the international H.324 standard.
Video conferencing over the Internet or Local Area Network appears likely to supersede the POTS system, although POTS equipment still offers a cost-effective, viable option.
IP or LAN video conferencing
Many companies and agencies now have elaborate LANs and are making use of desktop video conferencing to run projects between sectors or divisions where personnel are located at great distance from each other, and are able to use the audio and video for interacting and progressing their work. Two or more sites are able to link over the Internet or via a LAN to collaborate using desktop video conferencing while sharing applications. There are many IP video conferencing products available.
Web Video Conference
The web video conference can actually mean a series of different things, all of which should be offered by your conference call service. For example, a popular form of web conference calls involves application sharing. This allows a conference leader to turn his or her desktop over to other conference participants.
Application sharing in the web video conference actually works both ways. Everyone on these web conference calls gains access to one another's desktop, and can take control of each other's cursors in order to open and work on files. While this is very handy when several people are working on a single document or project, it can get unwieldy if too many people are in on the conference.
Conference calls providers usually also offer another web video conference, called application showing. In this case, no one has control over anyone else's computer. Instead, these conference calls simply allow everyone to view on their screens exactly what the host is doing on his or her computer.
These web conference calls are a great way for people to work together, without having to email files back and forth. While email is a wonderful thing, it's far too easy for people to lose track of which copy of a file holds the latest changes. By using web conferencing, all participants can have input on a file at the same time, thus ensuring that everyone is heard.
Point-to-Point Conferencing
Conferencing between two sites is termed point-to-point and is the most frequently used method. It only requires equipment at each site and the network of choice.
Multi-Point Conferences
There are times when more than two sites wish to communicate together using video conferencing. This can be achieved by the use of a video bridge. Video bridges are specialized systems that enable several video conference sites to dial in together. At a receive site, the user will see their own local picture and a set of pictures showing all the other participating sites. In this kind of situation it is advisable to designate a chairperson who can ensure that one site speaks at a time, to avoid confusion!
Voice Switched Conferences
Multipoint conferences introduce additional constraints. With point-to-point conferences both sites can see and hear each other throughout the conference. With multipoint e.g. with eight sites it would be unworkable for all sites to be seeing all other sites simultaneously so normally the conference is voice switched, in other words the image of the site speaking takes precedence and is seen by all the other sites.
Sharing Applications
Imagine you have a colleague who is working with you on an important piece of written work. You are both using a word processor on personal computers in your respective offices. Unfortunately, your colleague is 500 miles away in another part of the country, and it is impossible to travel to meet each other regularly. The solution...
...application sharing through video conference.
With most videoconference systems, users are able to share the software they are using with a remotely connected site. This means that if you are using Excel spreadsheet version 97, you can share the work stored on this software with your partner, and both of you can move around in the spreadsheet, adding, modifying, saving and printing, whilst you discuss the work.
Desktop conference
This is where a camera sits on top of your desktop VDU and connects through telephony to other desktop computers with similar equipment attached.
Modes of videoconference
There are also four types of viewing modes with video conferencing:
1. Automatic, Voice Activated Mode--In this mode, automatic switching between the sites is activated by the predominant audio site. Endpoint locations view the location currently speaking. The speaking location views the previous talking location. All locations continue to hear the conference at all times.
2. Chair Control Mode--In this mode, the "conference chair" determines which location will be viewed by all the other locations and at what time during the course of the conference. This is very helpful when a moderator is conducting a conference and wishes to target particular locations for a question or response.
3. Broadcast/Presentation Mode--This mode provides for a single endpoint location (the broadcaster or presenter) to continuously be viewed and heard by all other endpoint locations throughout the duration of the conference. In this mode, switching among sites will not occur. A good application for this mode is the presentation of an annual report by a CFO to the stockholders or an announcement to employees by the president of the company.
4. Continuous Presence--To utilize this mode, all participating sites must subscribe to the feature. Up to four sites may be viewed on the monitor simultaneously. A good application for using this mode is a meeting/class involving multiple sites.
Access type
When images are transported from location to location, they are transmitted over a medium known as the network. Access to the network can be over a variety of methods and bandwidths or transmission speeds which affect the picture quality as well as the cost of the video conference. The higher the speed or bandwidth, the better the quality and the higher the cost. Most video conferences today are conducted at 384 kilobits per second (kbps), but other speeds are available from 112 kbps, 786 kbps, up to a full T-1 (1.544 megabits per second or mbps).
There are two methods to access the network for video conferencing: dial and dedicated. Dial access treats a video call very much like a normal voice telephone call. A video call always travels through the local telephone company central office and is routed to the long distance network or LINC if long distance transport is required. An ISDN Basic Rate Interface (ISDN-BRI) is used most frequently for dial video conferences at 384 kbps. ISDN subscribers have no geographic limitations and thus have global accessibility anywhere ISDN is provided. Dedicated access utilizes a T-1 circuit via lines provisioned through VNS.
There are advantages to both types of access as shown below:
| Dial Access | Dedicated Access |
| Good for small to medium-sized conferences held occasionally during the day. | Good for high-volume usage. |
| Good for connecting to video conferences outside of the State. | Good for video conferences held primarily within the State. |
| Good for lower bandwidth speed conferences. | Good for higher (or full range) bandwidth speed conferences. |
Advantages of Videoconference
Better Planning: Planning ahead is an essential part of the video conference. The preparation time yields big returns when students and teachers are well prepared for the exchange of information.
Interaction with Experts: Students are able to get answers to questions from experts who, because of time and distance, would otherwise be inaccessible.
Learn about cultural differences: Students are able to interact with other students and adults who may be very different from themselves.
Addresses different Learning Styles: It can include media such as video clips, animations, audio and graphics. This first hand learning is especially good for visual learners.
Increases Motivation: You will find that students are much more willing to do the research when they know that they will be presenting it to other classes. Most students enjoy using the new technology.
Better Retention: Students are learning from a primary source rather than a textbook.
Improve Skills:
- Presentation and Speaking Skills
- Communication and Management Skills
- Questioning Skills
Other advantages include:
- Convenience;
- Cost savings for travel, accommodation and staff time;
- Ability to link several sites simultaneously;
- Access to remotely located experts;
- In child abuse or other court proceedings the presentation of victims’ evidence via videoconferencing can reduce the potential of intimidation.
- Time savings
Having a set time for the meeting also encourages more control and less time wasted on non-agenda items.
Research has suggested that videoconferencing is very successful when there is a clear communication need that cannot easily be met using other media. While users feel that video conference meetings do not have the flow and momentum of face-to-face meetings they are seen to be particularly good for:
- Dealing with routine matters
- Dealing with non-controversial issues
- Quick informal meetings at short notice
- Imposing a structure on meetings
Disadvantages of Videoconference
These can include:
· The quality of the received images can be compromised by the technology;
· On lower quality links movement can be jerky;
· Body language can be lost if movement is jerky and/or picture quality is reduced;
· There can be a delay on the sound that participants need to get accustomed to;
· Some believe that the atmosphere of a normal face-to-face meeting is lost.
Certainly some of these disadvantages are true especially for the lower quality links. For meetings it is said that if you already know the participants it is a distinct advantage. This is probably true for most meetings but especially for videoconferences if the technical quality is compromised.
What are they not good for?
Video conferencing is not suitable for everything; if you are planning any of the following activities then a face-to-face meeting is likely to be more successful:
- Selling new ideas
- Complicated tasks
- Influencing people
- Tasks involving innovative interaction
- Confidential meetings
- Tasks which involve a high social component
- Negotiations
- Meetings involving a lot of paper
- Highly controversial meetings
Application of Videoconference
Meetings
This is probably the most popular application. The cost savings can be appreciable especially for international conferences where not only the travel costs are saved but also the significant time spent traveling to destinations. Take for example a research project involving collaborators in the
In some cases this “travel replacement” can actually act as a disincentive to videoconference as, despite the real costs and inconvenience of travel, some people actually enjoy the travel experience, especially when someone else is footing the bill.
Interviews
This is another use that is growing in popularity. It is found by many users to be just as effective as face-to-face interviews particularly when data sharing is used to compare CVs etc. For international interviews, videoconferencing could include candidates that previously would have been excluded purely on grounds of cost. Some interviewers regard the conference experience as quite inferior when compared to a face-to-face meeting and complain that the medium lacks spontaneity, and that nuances of body language are lost. This is true up to a point.
Other interviewers use videoconferencing as a first stage filter in the selection process. They are thus able to view many more potential candidates due to the cost savings, especially where these applicants are based overseas.
Teaching
Videoconferencing can open up new dimensions to teaching. Small group seminar teaching is a common use and functions in a similar way to videoconference meetings. The extra dimension introduced by sharing, for example, PowerPoint data between sites helps to give the remote audience the same teaching experience as the local students. With videoconferencing the subject specialist no longer has to be in the same room as the students. An international expert can be linked to a number of sites simultaneously around the world. Several sites can also collaborate to present a subject more comprehensively: a cancer specialist could introduce a patient at one site and demonstrate the manifestations of the disease; at another, the pathology laboratory could show histology slides; and a third location could demonstrate relevant surgical procedures from an operating theatre. The program could be linked to local, national and international audiences with interaction from each. This is a hypothetical example but does illustrate the added value that structured videoconferencing can bring to clinical teaching.
Videoconferencing teaching sessions can take many forms including:
- A lecturer in a studio teaching remotely to a group of students;
- A lecturer teaching students locally and also relayed to a remote audience;
- A lecturer teaching local and remote students with full interaction.
In the first scenario the lecturer can adopt a seating position in a typical meeting configuration (Figure). They can select appropriate sources i.e. camera, visualiser, video cassette player, as needed for the presentation, and can also interact with the remote site in the same way that would occur during a videoconference meeting.
In the third scenario, where teaching is being conducted both locally and remotely and full interaction is needed, the situation is more complex. Pictures and sound are now required from the remote site. The local students and the lecturer will need to see and hear the remote students. A second television display facing the students will normally be provided but the lecturer also requires a second preview monitor in the lectern facing them in order to view the remote students.
Both figures show television monitors, but in many cases data projectors will be utilized for the student displays as the images can be much larger than television monitors and still be acceptably bright under ambient lighting levels. However care has to be taken with some data projectors, as the noise from their cooling fans can be quite intrusive.
In
Management
Colleges with split campuses need to communicate regularly and efficiently. Videoconferencing is seen as a cost-effective solution. Some of the most regular users of videoconferencing fall into this category.
Remote Diagnosis
This can be useful where specialist medical resources are scarce e.g. in a rural area cottage hospitals and GP surgeries can be linked to the regional teaching hospital. Patients can then receive a rapid specialist diagnosis.
A particular project sponsored by BT enables paramedics to relay instant pictures of accident scenes to the hospital Accident and Emergency department so that they can give advice to the medical staff and prepare facilities for the victims, prior to their arrival.
Legal work
The nature of many legal cases can involve communication between parties in different locations, even different continents. Videoconferencing helps to reduce costs. It is also being used for live into court sessions. In particularly sensitive cases e.g. involving child abuse and rape, new legislation is expected to encourage videoconferencing to make the experience far less traumatic for the victims.
At the
Video conferencing is set to save teaching staff a great deal of time which would have been taken up traveling by rail or road from one site to another.
The University is using a combination of digital satellite television and video conferencing to connect its dispersed student groups around the region.
Videoconferencing technology can be used to enable remote students to call back into the studio whilst a live program is 'on air' and ask questions of the guests and experts (See the diagram above). This technique has been successfully used in the last few years in many of the university's live TV transmissions.
With increased bandwidth and greater transmission speeds now becoming available, it will not be long before academics in any part of the university will be able to enter their local videoconference suite and broadcast a live program to anywhere in the world.
Conclusion
Videoconferencing does use fairly complex technology to achieve its aim of enabling communication. A user however does not require technical knowledge to take advantage of the medium. Hopefully this paper helps to bridge the gap between being a complete novice and having sufficient understanding to realize the potential of videoconferencing.
While background reading can be useful there is no substitute for experience and the reader is strongly urged to experience videoconferencing first hand by taking part in conferences.
Using videoconferencing as a tool for screening candidates for positions at
Future
Several commercial companies are developing new ways of using video conferencing in education. One of the most recent developments is to incorporate video conferencing into web-based systems.
A web-based system using streaming video multi-casting is now reaching the education sector. Teachers and presenters can sit in their own office or in a nearby studio and present a 'live' lecture in front of a camera attached to a web server. Using a simple switching device and several cameras, the presenter can provide remote participants with graphics, whiteboard, flipchart and other visual aids as well as alternative views of the local classroom, lecture room, etc.
These images and sound are subsequently 'web cast' - sent via the Internet to anyone who wishes to take part. Alongside the video images and sound is a MS PowerPoint presentation or other graphical sequence transmitted in a .gif file format. Synchronizing software enables the graphic images and presentation materials to reach the viewers at the same time the presenter verbally cues them.
Beneath the tutor's video images is a text-messaging box where students and participants can offer comments, ask questions, and receive responses from the presenter in real time. Research has shown that remote students are more likely to participate in such a discussion when they are 'anonymous'.
TO DOWN LOAD REPORT AND PPT
